At least 24 people were killed and more than 200 injured in the worst sectarian violence since the uprising that ousted Hosni Mubarak in February.

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The rioting lasted late into the night, bringing out a deployment of more than 1,000 security forces and armored vehicles to defend the state television building along the Nile, where the trouble began. The military clamped a curfew on the area until 7 a.m.

The clashes spread to nearby Tahrir Square, drawing thousands of people to the vast plaza that served as the epicenter of the protests that ousted Mubarak. On Sunday night, they battled each other with rocks and firebombs, some tearing up pavement for ammunition and others collecting stones in boxes.

At one point, an armored security van sped into the crowd, striking a half-dozen protesters and throwing some into the air.

Protesters retaliated by setting fire to military vehicles, a bus and private cars.

After midnight, mobs roamed downtown streets, attacking cars they suspected had Christian passengers. In many areas, there was no visible police or army presence to confront or stop them.

Christians, who make up about 10 percent of Egypt’s 80 million people, blame the country’s ruling military council for being too lenient on those behind a spate of anti-Christian attacks since Mubarak’s ouster. As Egypt undergoes a chaotic power transition and security vacuum in the wake of the uprising, the Coptic Christian minority is particularly worried about the show of force by ultraconservative Islamists.

Prime Minister Essam Sharaf, addressing the nation in a televised speech, said the violence threatened to throw Egypt’s post-Mubarak transition off course.

“These events have taken us back several steps,” he said.

“Instead of moving forward to build a modern state on democratic principles we are back to seeking stability and searching for hidden hands - domestic and foreign - that meddle with the country’s security and safety.”

“I call on Egyptian people, Muslims and Christians, women and children, young men and elders to hold their unity,” Sharaf said.

The Christian protesters said their demonstration began as a peaceful attempt to sit in at the television building. But then, they said, they came under attack by thugs in plainclothes who rained stones down on them and fired pellets.

“The protest was peaceful. We wanted to hold a sit-in, as usual,” said Essam Khalili, a protester wearing a white shirt with a cross on it. “Thugs attacked us and a military vehicle jumped over a sidewalk and ran over at least 10 people. I saw them.”

Wael Roufail, another protester, corroborated the account. “I saw the vehicle running over the protesters. Then they opened fired at us,” he said.

Khalili said protesters set fire to army vehicles when they saw them hitting the protesters.

Ahmed Yahia, a Muslim resident who lives near the TV building, said he saw the military vehicle plow into protesters. “I saw a man’s head split into two halves and a second body flattened when the armored vehicle ran over it. When some Muslims saw the blood they joined the Christians against the army,” he said.